Two-dimensional Self-consistent Fluid Model Research Articles

Discharge efficiency in high-Xe-content plasma display panels

We study theoretically the overall output performance and the dominating reaction processes of the vacuum ultraviolet (UV) radiation production in high-Xe partial pressures in plasma display panels (PDPs) with Ne–Xe gas mixtures. A two-dimensional self-consistent fluid model is applied for the simulations of discharges and UV radiation in sustaining phases of PDPs. The UV intensity increases with the Xe partial pressure (PXe). The discharge efficiency also increases with PXe. The resonant radiation from Xe(3P1) dominates for 3.5%, while that from Xe2(3Σu+) becomes dominant over Xe(3P1) for 10%–30%. Remarkably for 30%, the intensity from Xe2(1Σu+) is even larger than that from Xe(3P1). It is found that for higher PXe, the UV radiation mainly consists of the excimer radiation from Xe2(1Σu+) and Xe2(3Σu+). Here, Xe(3P1) does not play a role itself as the UV radiator of the resonant radiation (147 nm), but as the precursor to Xe2(1Σu+), which results in the excimer radiation (173 nm).

Modeling of a capacitively coupled radio-frequency methane plasma: Comparison between a one-dimensional and a two-dimensional fluid model

A comparison is made between a one-dimensional (1D) and a two-dimensional (2D) self-consistent fluid model for a methane rf plasma, used for the deposition of diamond-like carbon layers. Both fluid models consider the same species (i.e., 20 in total; neutrals, radicals, ions, and electrons) and the same electron–neutral, ion–neutral, and neutral–neutral reactions. The reaction rate coefficients of the different electron–neutral reactions depend strongly on the average electron energy, and are obtained from the simplified Boltzmann equation. All simulations are limited to the alpha regime, hence secondary electrons are not taken into account. Whereas the 1D fluid model considers only the distance between the electrodes (axial direction), the 2D fluid model takes into account the axial as well as the radial directions (i.e., distance between the electrodes and the radius of the plasma reactor, respectively). The calculation results (species densities and species fluxes towards the electrodes) obtained with the 1D and 2D fluid model are in relatively good agreement. However, the 2D fluid model can give additional information on the fluxes towards the electrodes, as a function of electrode radius. It is found that the fluxes of the plasma species towards both electrodes show a nonuniform profile, as a function of electrode radius. This will have an effect on the uniformity of the deposited layer.

Metastable argon density evolution in a pulsed ICP discharge

A two-dimensional self-consistent plasma fluid model was developed to study the dynamics of a pulsed power inductively coupled argon discharge. The metastable Ar*(/sup 3/P/sub 0/ and /sup 3/P/sub 2/ levels) density evolution during a pulse is governed by volumetric reactions, giving rise to complex spatiotemporal behavior.

Two-dimensional simulation of a pulsed-power electronegative discharge

A two-dimensional self-consistent fluid model was developed to study the spatio-temporal dynamics of a pulsed power (square-wave modulated) inductively coupled electronegative (chlorine) discharge. The coupled equations for plasma power deposition, electron temperature, and charged and neutral species densities were solved simultaneously to capture the spatio-temporal evolution of the discharge. Simulation results showed separation of the plasma into an electronegative core and an electropositive edge during the active glow (power on) fraction of the cycle, and the formation of a positive ion/negative ion (ion-ion) plasma in the afterglow (power off) fraction of the cycle. During the early active glow, the negative ion flux is convection dominated near the quartz window under the planar coil of the ICP reactor. This is due to the emergence of relatively large electrostatic fields, leading to a self-sharpening negative ion front propagating into the plasma.

Energy loss mechanisms in the microdischarges in plasma display panels

Low luminous efficacy is one of the major drawbacks of plasma display panels (PDPs), where the main limiting factor is the efficiency of the microdischarges in generating UV radiation. In this work we use a two-dimensional self-consistent fluid model to analyze the energy loss mechanisms in neon–xenon discharges in coplanar-electrode color PDPs and interpret experimental data on the luminous efficacy of these PDPs. The modeling results are in good agreement with the measured UV emission spectrum and measured trends in the efficacy. Most of the electrical input energy is transferred to ions and subsequently to the gas and the surface. The electrical energy transferred to electrons is mostly used for ionization and excitation, where the part used for xenon excitation largely ends up in UV radiation. The amplitude, frequency, and rise time of the driving voltage mainly affect the energy losses due to ion heating. The xenon content also affects the conversion of electron energy into UV energy.

Two-dimensional, self-consistent, three-moment simulation of RF glow discharge

A two-dimensional self-consistent nonequilibrium fluid model is used to simulate radio frequency (RF) glow discharges to evaluate the quantitative effects of the radial and axial flow dynamics inside a cylindrically symmetric parallel-plate geometry. This model is based on the three moments of the Boltzmann equation and on Poisson's equation. Radial/axial flow dynamics of plasma in low-pressure parallel plate RF glow discharges are investigated. Instead of uniform profiles along the radial direction, which are assumed in one-dimensional models, nonplate profiles are obtained from the two-dimensional simulations. Ionization rate and three moment distributions of plasma density, average velocity, and mean energy are presented in a two-dimensional configuration. The maximum ionization rate occurs in the radial sheath region and agrees with experimental results. Variations in ion density distributions at different positions, various gas pressures frequencies, and applied fields are discussed. >

Radial flow effects in a multidimensional, three-moment fluid model of radio frequency glow discharges

For the first time, a two-dimensional self-consistent nonequilibrium fluid model is used in simulations of rf glow discharges to evaluate the quantitative effects of the radial and axial flow dynamics inside a cylindrically symmetric geometry. Electrons are modeled with a three-moment nonequilibrium model and ions are modeled with a nonequilibrium single-moment model which includes an ionic effective electric field. The nonuniform plasma density profiles and the radial sheath width variation with various gas pressures are discussed. These resulting radially nonuniform plasma density profiles are an important issue for plasma processing.